Carrier relaying apparatus



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I Fault SensingReloy Relay Circuit Breaker WITNESSES:

United States Patent Ofifice CARRIER RELAYING APPARATUS John C. G. Carter, Baltimore, Md, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a con poration of Pennsylvania Application June 30, 1953, Serial No. 365,153

4 Claims. (Cl. 317-48) My invention relates to carrier relaying apparatus, and particularly to control circuits for keying the carrier transmitter in response to various conditions.

It is a general object of my invention to provide an improved keying control circuit for carrier relaying apparatus.

Another object of my invention is to provide an improved carrier relaying control circuit wherein the opera.- tion of some contacts will start the transmitter carrier and disable auxiliary functions, while the operation of other contacts will start the transmitter carrier without disabling auxiliary functions.

Another object of my invention is to provide an improved carrier relaying keying control circuit wherein the operation of some contacts will start the transmitter carrier and disable auxiliary functions, while operation 9 of other contacts will stop transmitter carrier without enabling auxiliary functions.

These and other objects are effected by my invention as will be apparent from the following description taken in accordance with the accompanying drawing, forming a part of this application, in which the single figure is a schematic circuit diagram showing a preferred embodiment of my invention.

In the drawing, a conventional power line carrier type transmitter 11 is shown in block form. The transmitter comprises an oscillator 13, a modulator 15, a keyed stage 17, and a power amplifier 19. The details of such a trans mitter are Well known in the art, and since they form no part of the invention, it is considered superfluous to show them herein. The output of the carrier transmitter 11 is connected through the usual coupling arrangement 21 to one conductor 23 of a commercial high-tension power line section. The power line conductor is connected through a conventional line trap 25 and circuit breaker 27 to the junction 31 of two power line sections. Shown inductively coupled by means of potential and current transformers to the power line conductor 23 between the junction 31 and the circuit breaker 27 are a fault sensing relay 33 and a directional relay 35 respectively. Such relays are well known in the art, are commercially available, and the details of their construction need not be discussed herein. It is only necessary to state that the fault sensing relay 33 has a normally closed contact 37, and the directional relay 35 has a normally open contact 40. The term normally open or normally closed contact as used herein refers to the contact position when the apparatus is in standby condition as shown in the drawing.

The improved keying control circuit shown in the drawing is responsive to the fault sensing and directional relays, and operates to control the keying of the carrier transmitter 11. The'keying circuit comprises first and second output terminals 39, 41 which are respectively connected to the anode 43 and cathode 45 of a keyer tube 47 which is connected in the keyed stage 17 of the transmitter 11. it is understoodthat the transmitter keyed stage may take many forms, andthe showing of the keyer 2,806,184 Patented Sept. 10, 1957 tube connection is for illustrative purposes only. The first output terminal 39 is connected through a voltage dropping resistor 49 to a third terminal 51 which is adapted for connection to the positive terminal 13+ of a direct-current power supply (not shown). The second output terminal 41 is common to a fourth terminal 53 which is adapted for connection to the negative terminal B of said direct-current power supply (not shown). The first output terminal 39 is also serially connected through the normally closed contact 55 of an auxiliary function relay 57, a rectifier 59, a single-pole push-button switch 61, and the normally closed contact 37 of the fault sensing relay 33 to the second output terminal 41. The rectifier 59 is poled to conduct in the direction from the first output terminal 39 to the second output terminal 41. The normally open contact 40 of the directional relay 35 is connected to shunt said first and second output terminals 39, 41. An auxiliary function disabling relay 63 has its energizing coil 65 connected between the third terminal 51 and the junction 68 of the rectifier 59 and the push-button switch 61. One auxiliary function device shown in the drawing is a telephone handset 67 which is connected to a conventional amplifier 69, the output of which is connected through a normally closed contact 71 of the auxiliary function disabling relay 63 to the modulator stage 15 of the carrier transmitter 11. The energizing coil 73 of the auxiliary function relay 57 has one side connected to said second terminal 41 and the other side connected through a normally open contact 75 to the said third terminal 51. The normally open contact 75, just mentioned, is actuated when the auxiliary function is put to use. In the case shown, this contact is closed when the push-to-talk switch of the telephone handset 67 is depressed. Another auxiliary function device shown is the sleet detector. The sleet detector is associated with a carrier receiver 83 comprising a plurality of conventional frequency selective tuned circuits 89 and a conventional detector stage 82. The tuned circuit input is connected via conductor 86 to the line tuner 21. The tuned circuit output is connected through a resister 81 to the signal grid circuit of a tube in the detector 82. The resistor 81 is shunted by the normally closed contacts 84 of a sleet detector relay 91, and also by the normally open contact 85 of the disabling relay 63. The operation of the sleet detector function will be hereinafter more fully explained. As will be clear to those skilled in the art, particularly upon reading the description of operation following, numerous auxiliary functions in addition to those shown could be used. Some of these are telemetering, load control, and supervisory control. For each such additional auxiliary function, it is only necessary to insert an additional normally open contact in parallel with the contact 75, and to add a normally closed disabling contact to the armature of the auxiliary function disabling relay 63.

The operation of the improved keying control circuit will now be explained. Under standby conditions, the directional relay contact 40 is open, the fault sensing relay contact 37, the auxiliary function relay contact 55, and the push-button switch 61 are closed. Current flows from the positive direct-current power supply terminal 51 through the voltage dropping resistor 49, the normally closed contact 55 of the auxiliary function relay 57, the rectifier 59, the push-button switch 61 and the normally closed contact 37 of the fault sensing relay 33 to the negative terminal 53 of the power supply. The first output terminal 39 is now substantially at power supply negative potential, since the forward resistance of the rectifier 59 is low compared to that of the voltage dropping resistor 49. Therefore, the keyer tube 47 has no plate voltage, and the transmitter carrier is shut off. At the same time, current flows from the positive power supply terminal 51 through the energizing coil 65 of the auxiliary function disabling relay 63, the push-button switch 61, and the closed contacts 37 of the fault sensing relay 33'to the power supply negative terminal 53. The coil 65 of the auxiliary function disabling relay 63 is, therefore, energized, its contact 71 is closed, and the auxiliary functions are enabled. If an auxiliary function is now initiated, as by using the telephone handset s7, the auxiliary function relay energizing coil 73 is energized and the auxiliary function contact 55 is opened. This in effect disconnects the first output terminal 39 from the power supply negative terminal 53, and brings it to substantially power supply positive potential. The keyer tube 47 now has normal plate voltage, and the transmitter carrier is now turned on. Opening of the auxiliary function relay contact 55 had no effect on the energizing coil 65 of the auxiliary function disabling relay 63, so that all auxiliary functions are still enabled. If a fault now appears on the transmission line, the fault sensing relay contact 37 opens. Opening of the fault sensing relay contact at this time does not effect the potential of the first output terminal 39, or the keyer tube 47, but it opens the circuit of the energizing coil 65 of the auxiliary function disabling relay 63. This causes all auxiliary functions to be disabled. If the fault is of a kind to require the transmitter carrier to be stopped, the contact 443 of the directional relay 35 closes. This connects the first output terminal 39 to the negative power supply terminal 53, which removes the anode voltage from the keyer tube 47, causing the transmitter carrier to stop. Since at this time, the contact 37 of the fault sensing relay 33 is open and since current cannot flow through the now open contact 55 and rectifier 59, the energizing coil '55 of the auxiliary function disabling relay 63 is still de-energized, and all auxiliary functions remain disabled.

If an auxiliary function is not in use at the time the fault sensing relay 33 operates, the coil 65 of the dis abling relay will still be de-energized by the opening of the fault sensing relay contact 37. If the directional relay now closes its contact 40, it will stop the carrier transmitter by bringing the first output terminal to B potential, but it will not bring the potential of junction 68 to B- potential which would re-energize disabling relay coil 65 and re-enable auxiliary functions, because the rectifier 59 will not conduct in the reverse direction. The push-button switch 61, in the location shown, can be used to start transmitter carrier for test purposes, and at the same time disable the auxiliary functions. This switch could equally well be placed between the rectifier 59 and the contact 55 of the auxiliary function relay 57, in which case it would be used to start a transmitter carrier without disabling the auxiliary functions. In either case, the opening of the fault sensing relay contact 37 and the closing of the directional relay contact 40. for the appropriate kind of fault, will remove plate voltage from the keyer tube 47, step the transmitter carrier, and disable all auxiliary functions.

The sleet detection function introduces resistance into the carrier receiver circuit which makes the receiver less sensitive. When a fault occurs and the fault sensing relay 33 operates, the receiver 83 must be returned to full sensitivity. When the sleet detector is in operation, the contact 84 of the sleet detector relay 91 is open, so the resistor 81 is inserted in the detector tube grid circuit 80, reducing the sensitivity of the receiver 83. When the fault sensing relay 33 opens its contact 37, the disabling relay coil 65 is de-energized, and contact $5 closes to short the resistor 31, returning the receiver 83 to full sensitivity.

It will be understood by those skilled in the art that numerous types of protective relaying schemes are well known, and that the type of relay actually used to perform the functions of the fault sensing relay and the directional relay, shown by the drawing, will depend upon the particular protective relaying scheme selected.

While I have shown my invention in only one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible to various changes and modifications without departing from the spirit thereof.

I claim as my invention:

1. In a communication system, carrier relaying apparatus including a carrier relaying transmitter having a keyed stage, a keyer control circuit comprising first and second output terminals connected to control said keyed stage, third and fourth terminals adapted for connection respectively to positive and negative terminals of a direct current power supply, a resistor connected between said first and third terminals, a connection between said second and fourth terminals, a first normally closed contact, a rectifier, a second normally closed contact, means serially connecting said first contact, said rectifier and said second contact between said first and second terminals, said rectifier being poled to conduct in the direction from said first to said second terminal, a normally open contact connected when closed to shunt said first and second terminals, means for selectively changing the position of said first normally closed contact, and means for controlling the position of the second normally closed contact and the normally open contact in accordance with the existence of certain predetermined conditions in said communication system.

2. In a power line carrier system, a carrier relaying transmitter having a keyed stage, a keyer control circuit comprising first and second output terminals connected to control said keyed stage, a direct-current power sup ply, third and fourth terminals adapted for connection respectively to positive and negative terminals of said direct current power supply, a resistor connected between said first and third terminals, a connection between said second and fourth terminals, a first normally closed contact, a rectifier, and a second normally closed contact serially connected between said first and second terminals, said rectifier being poled to conduct in the direction from said first to said second terminal, a first normally open contact connected when closed to shunt said first and second terminals, apparatus for actuating said transmitter to transmit signals other than keyed signals, a relay energizing coil connected between said third terminal and the junction of said rectifier and said second normally closed contact for controlling operation of said apparatus, means responsive to operation of said apparatus to open said first normally closed contact to start said carrier transmitter without affecting said relay energizing coil, means responsive to a' predetermined condition of the power line carrier system for opening said second normally closed contact to start said carrier transmitter and de-energize said relay energizing coil to thereby disable said apparatus, and means responsive to a predetermined condition of'said power line carrier system for closing said first normally open contact to stop said transmitter without affecting said relay energizing coil.

3. In combination with a transmitter for a power line carrier system, apparatus for developing a control voltage for said transmitter comprising first and second output terminals connected to said transmitter, a direct-current power source, a resistor connecting said first output terminal to the positive terminal of said power source, a connection between the negative terminal of said power source and said second output terminal, a pair of electron paths c'onnected to shunt said output terminals, one of said paths including first and second normally closed contacts, the other of said paths including a normally open contact, means for selectively altering the position of said first normally closed contact, and means responsive to certain predetermined conditions in said carrier system for controlling the position of said normally open contact and said second normally closed contact.

4. In a communication system including a transmitter having a keyed stage, a modulator for said transmitter, a device for supplying a modulating voltage to said modulator, a connection between said device and said modulator, and apparatus for controlling operation of said transmitter, said apparatus comprising first and second output terminals connected to said keyed stage, a source of direct-current voltage, an impedance element connecting said first output terminal to one terminal of said voltage source, a connection between said second output terminal and the other terminal of said voltage source, relay means connected between said output terminals for shunting the output terminals in response to the existence of one or more predetermined conditions in said communication system, and a relay device connected between the terminals of said voltage source for breaking the connection between said modulator and said device in response to the existence of one of said predetermined conditions in said communication system.

References Cited in the file of this patent UNITED STATES PATENTS 1,765,887 Scott et a1. June 24, 1930 

